Super resin polish only gives short term protection both HD wax and Extra gloss protection will seal the paintwork and last a long time
(in terms of EGP your looking at at least 4-5 months) cant comment on HD as i have only just started using it.....
EGP is a Synthetic sealant where as HD wax is a erm wax,,
if it was me i would polish the car with super resin polish....
then treat with EGP (leave for an hour to cure as its easier to remove the longer its left)
then next day treat with HD wax (it gives a much better wetter looking finish than EGP)